A concern about radioactive materials has increased in Korea due to the Fukushima nuclear power plant accident in Japan. However, in fact, since the radioactive materials are used in fields such as nuclear power generation or nuclear weapons but used in hospitals, the radioactive materials are not always harmful. Particularly, a treatment method for thyroid cancer using a radioactive iodine isotope based on characteristics of thyroid cells absorbing iodine to thereby be differentiated, which is one of the treatment methods that are mainly used at present, has significantly contributed to increasing a complete cure rate of thyroid cancer. However, it is difficult to treat and dispose the radioactive material as the same method of general waste, the development of a technology of safely treating radioactive wastewater or materials generated after using radioactive isotopes in the nuclear power plants or hospitals has been demanded.
As the radioactive iodine, there are various kinds of isotopes, but the radioactive iodine exists in wastewater as iodine-125, iodine-129, iodine-131, iodine-132, iodine-133, or the like. Among them, iodine-131, iodine-132, and iodine-133, and the like, have short half-lives, such that radioactivity may be attenuated by storing the wastewater for a predetermined period. However, since a generation amount of radioactive wastewater containing iodine compounds is excessively large, realistically, there is a limitation in storing the wastewater itself in a water collecting tank for a long time. In addition, a half-life of iodine-125 emitting low energy gamma rays to thereby be used for medical applications is 60 days, which is not short, and in consideration of stability depending on the half-life, iodine-125 should be stored for 2 years or more. Further, in the case of iodine-129, a half-life thereof is 15.7 million years, such that attenuation of radioactivity by storing iodine-129 is almost impossible, and in the case of intake of iodine-129 in a human body, iodine-129 becomes concentrated in the human body and continuously releases radiation, such that iodine-129 is significantly harmful.
As the existing treatment method of radioactive wastewater in order to solve the problems as described above, there are a solidification treatment method, an ion exchange resin method, a coagulation precipitation method, and the like.
The solidification treatment method is a method of adding iodine into a material capable of being solidified such as asphalt, or the like, to block iodine. However, in this case, there is a disadvantage in that at the time of solidification treatment, iodine molecules or organic iodine compounds is easily emitted by internal heat in materials.
Further, in the ion exchange resin method, iodine is adsorbed and separated by filtering wastewater through an ion exchange resin, but there are disadvantages in that iodine removal efficiency is low, a large amount of waste is generated, which increase cost, and it is not easy to store the large amount of waste.
The coagulation precipitation method is a method of converting iodine into silver iodide by adding silver nitrate into wastewater and then precipitating the silver iodide, but there is a problem in that since a cost of silver nitrate is significantly high, a treatment cost is excessively consumed.
Otherwise, there is a method of using activated carbon as in Korean Patent No. 10-1046433, but similarly to the ion exchange resin method, there is a disadvantage in that it is difficult to adsorb and separate an iodide oxide. In addition, since the activated carbon should be frequently replaced, a replacement cost is high, and a volume of waste activate carbon or waste ion exchange resin in which radioactive iodine is adsorbed is large, such that a separate treatment space is required, and cost is also increased. Further, in the case in which wastewater contains highly concentrated radioactive iodine, there is a limitation in using the above-mentioned adsorption method.